During excitation and turn-on of a no-load transformer, it is likely that, because of a magnetic saturation characteristic of a transformer core, an excitation inrush current several times larger than the rated current occurs to causes voltage fluctuations and unnecessary trips relays. To suppress the excitation inrush current, a breaker needs to be turned on in a voltage phase in which a residual magnetic flux remaining in the transformer core after interruption and a steady magnetic flux (an alternating magnetic flux generated when a rated voltage is applied to the transformer) match. For example, there is disclosed a technology for storing a phase of an alternating-current voltage at a time of breaker opening and adjusting output time of a breaker turn-on signal such that, at a time of the next turn-on, the breaker can be turned on in a phase same as the phase of the alternating-current voltage at the time of the breaker opening (e.g., Patent Literature 1).